Method and Apparatus for Allocating Bandwidth in a Wireless Communication System

ABSTRACT

Network resources can be allocated more efficiently to communication sessions in a wireless telecommunications network, by the method of—monitoring the traffic load in the uplink and downlink direction in the network,—for the at least one session, determining the parameters ul_ratio and dl_ratio, given as ul_ratio=ul_throughput/(ul_throughput+dl_throughput) dl_ratio=dl_throughput/(ul_throughput+dl_throughput) wherein ul_throughput is the throughput in the uplink for the at least one communication session and dl_throughput is the throughput in the downlink for the at least one communication session, and—allocate resources to the at least one session in dependence of the traffic load and ul_ratio and dl_ratio, by allocating resources in the uplink in dependence of the dl_ratio and/or allocating resources in the downlink in dependence of the ul_ratio.

TECHNICAL FIELD

The present invention relates to a control node as defined in thepreamble of claim 1 and to a method as defined in the preamble of claim9.

BACKGROUND AND PRIOR ART

Bandwidth is a limited resource in any wireless communication network.As mobile terminals become more and more common, the demand for wirelesscommunication capacity increases steadily.

Therefore, it becomes increasingly important to allocate the availablebandwidth in a wireless communication system in the best possible way,in order to use the available bandwidth as efficiently as possible.

U.S. Pat. No. 6,925,068 discloses a method for allocating bandwidth in awireless communication system. Time slots may be allocated in a flexibleway for uplink or downlink transmissions depending on the bandwidthneeds of a channel. Channel bandwidth asymmetry can be achieved in thesense that more time slots may be allocated in one direction than in theother direction (that is, more for downlink transmission than for uplinktransmission, or vice versa). The designation of any time slot can bechanged dynamically between uplink and downlink depending on therequirements. The decisions are based on reports of sessions that havebeen denied because of capacity problems.

U.S. Pat. No. 6,628,626 discloses a method for enabling high-speed datatransfer in the downlink direction by using an additional widebandcommunication channel from the base station to the mobile terminals.This principle is based on the assumption that the bandwidthrequirements are higher in the downlink direction than in the uplinkdirection. This is generally, but not always, correct.

WO 00/01188 discloses a method of allocating traffic channels to mobileterminals in dependence of various communication quality parameters inorder to allocate channels more effectively in the wireless network.

The scheduling algorithms known in the art do not consider that eachtraffic session is bidirectional and that a scheduling decision in onedirection will also affect the session behaviour in the other direction.

OBJECT OF THE INVENTION

It is an object of the invention to control the utilization of thecapacity in a wireless network in such a way that both the uplink andthe downlink capacity is maximized while avoiding congestion situations.

SUMMARY OF THE INVENTION

This object is achieved according to the present invention by a controlnode for use in a wireless communication network, for allocating networkresources to at least one communication session in the wirelesstelecommunications network, comprising resource allocation means forallocating resources to the at least one session in dependence oftraffic load information regarding the traffic load in the uplink anddownlink directions in the network, and an ul_ratio and a dl_ratio percommunication session for the at least one communication session, givenas

ul_ratio=ul_throughput/(ul_throughput+dl_throughput)

dl_ratio=dl_throughput/(ul_throughput+dl_throughput)

wherein ul_throughput is the throughput in the uplink for the at leastone communication session and dl_throughput is the throughput in thedownlink for the at least one communication session, and the resourceallocation means is arranged to allocate resources in the uplink independence of the dl_ratio and/or allocating resources in the downlinkin dependence of the ul_ratio.

The object is also achieved by a method of allocating network resourcesto at least one communication session in a wireless teleconmunicationsnetwork, comprising the steps of

-   -   monitoring the traffic load in the uplink and downlink direction        in the network,    -   for the at least one session, determining the parameters        ul_ratio and dl_ratio, given as

ul_ratio=ul_throughput/(ul_throughput+dl_throughput)

dl_ratio=dl_throughput/(ul_throughput+dl_throughput)

-   -    wherein ul_throughput is the throughput in the uplink for the        at least one communication session and dl_throughput is the        throughput in the downlink for the at least one communication        session, and    -   allocate resources to the at least one session in dependence of        the traffic load and ul_ratio and dl_ratio, by allocating        resources in the uplink in dependence of the dl_ratio and/or        allocating resources in the downlink in dependence of the        ul_ratio.

In contrast, prior art scheduling algorithms typically consider theuplink and the downlink independently of each other when making ascheduling decision.

The inventive idea is based on the fact that most traffic sessions havea deterministic behaviour. A session follows a deterministic signallingsequence because the two user terminals participating in the sessionhave agreed to a protocol (standardized or proprietary) in order to beable to communicate. According to the invention, the deterministicbehaviour for each traffic session is analyzed and this knowledge isused when performing a joint uplink/downlink scheduling decision. Thedeterministic behaviour is analyzed in a protocol-independent fashion,that is, no knowledge about any specific communication protocol isrequired.

In a preferred embodiment, the control node further comprises

monitoring means for obtaining traffic load information about thetraffic load in the uplink and downlink direction in the network, andcalculating means for the at least one session, determining theparameters ul_ratio and dl_ratio. Alternatively, the monitoring meansand calculating means may be implemented in separate units or in oneseparate unit outside of the control node.

The monitoring means may be arranged to identify any spare capacity inthe uplink and/or the downlink. In this case, the resource allocationmeans is arranged to increase the scheduling priority in the downlinkdirection for the at least one session, if spare capacity is detected inthe uplink direction and the at least one session has a high ul_ratio.Similarly, the resource allocation means may be arranged to increase thescheduling priority in the uplink direction for the at least onesession, if spare capacity is detected in the downlink direction and theat least one session has a high dl_ratio. These two functions may beimplemented together or just one of them may be used.

In some cases, the transmission of large amounts of data in the firstdirection is dependent on transmission of small amounts of data, such asacknowledgements, in the opposite direction. According to the inventionif there is spare capacity in the first direction, efficient use of thecapacity in the first direction is ensured because the small amounts ofdata in the opposite direction are given a higher priority. Thus, thewaiting time before data can be sent in the first direction is reduced,and the spare capacity is used more efficiently.

The monitoring means may arranged to identify overload or congestion inthe uplink and/or the downlink. In this case, the resource allocationmeans may be arranged to decrease the scheduling priority in thedownlink direction for the at least one session if overload orcongestion is detected in the uplink direction and the at least onesession has a high ul_ratio. Similarly, the resource allocation meansmay be arranged to decrease the scheduling priority in the uplinkdirection for the at least one session if overload or congestion isdetected in the downlink direction and the at least one session has ahigh dl_ratio.

The inventive method of reducing congestion in one direction bydecreasing scheduling priority in the opposite direction is beneficialfor two main reasons: Firstly, it provides a quicker way of providingfeedback to the presumed traffic generating source, that is, the sender.Also it leads to a smoother generation of the source traffic.

For example, for the transmission control protocol (TCP) a TCP sender issaid to be “ACK clocked” since it can only send data packets at the rateat which it receives ACKs. If only the priority in the data direction ofa bulk data transfer was decreased while maintaining the priority in theACK direction, the ACKs would, at least initially, continue to return atthe same rate. This might cause even more congestion in the datadirection since the TCP sender would continue to clock out data packetsat the same rate. On the other hand, decreasing the priority in the ACKdirection will lead to a reduced rate of ACKs, which will immediatelylead to a reduced transmission rate of data packets. This also reducesthe risk of further packet loss caused by congestion.

The detection of spare capacity on the one hand and overload orcongestion on the other hand may be implemented together, or just one ofthem may be used.

According to the invention, the overall throughput in the system isincreased so that both uplink and downlink capacity are used to theirmaximum extent, based on the current user traffic. Congestion can beavoided by smooth degradation of individual traffic flows. Instead ofdecreasing scheduling priority for the traffic in the congesteddirection, traffic session priority is decreased in the other directionfor sessions having a high throughput ratio in the congested direction.

Preferably, the calculating means is arranged to calculate the ul_ratioand the dl_ratio as average values over a certain period of time, forexample, as smoothed moving averages.

The inventive control node and method may be used in any type oftelecommunication network in which communication is performed across aradio interface. The invention will be particularly useful in networksin which the relationship between the uplink and the downlink capacitiescannot be changed easily.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following, by wayof example and with reference to the appended drawings in which:

FIG. 1 illustrates communication between two user terminals and a basestation in a wireless communication network.

FIG. 2 is a flow chart of the inventive method.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates a part of a wireless communication network,represented in FIG. 1 by a base station 1, communicating with a numberof user terminals 3 in a cell of the network. The two user terminals maybe engaged in two-way communication with each other, or with other unitsin the network, or may be uploading data to the network or downloadingdata from the network. The downlink communication from the base station1 to each of the terminals 3 is illustrated by arrows 5. The uplinkcommunication from the terminals 3 to the base station is illustrated byarrows 7.

The network also comprises at least one scheduling node 9 for schedulingthe traffic. This node is usually found in, or in connection to, thebase station 1. In FIG. 1 the scheduling node 9 is shown as part of acontrol node 11 introduced according to the invention. The control node11 also comprises a monitoring unit 13 arranged to monitor the trafficin the network, both in the uplink and downlink directions. The controlnode 11 also comprises a calculating unit 15 arranged to calculate theuplink ratio and the downlink ratio, as will be defined below, for eachcommunication session in the network, or in the cell.

Of course, the division of the control means into units is merely forillustrative purposes. The scheduling node 9, monitoring unit 13 andcalculating unit 15 may be software modules comprised in the samecontrol node 11 or may be implemented in separate units.

The scheduling node 9 will make scheduling decisions based on theinformation obtained according to the invention, possibly combined withother information used in the prior art. The priority informationobtained according to the invention will vary much more slowly than someof the other scheduling information, such as fast fading aspects.

In the situation shown in FIG. 1, for example, the network may have, ata given time, a high load on the uplink but a lot of spare capacity onthe downlink. If, in this case, one terminal 3 wishes to download anobject using TCP, the problem occurs that acknowledgement messages fromthe terminal 3 must compete with all the other uplink traffic, eventhough the average uplink bitrate required by the first terminal isfairly low. In this case the downlink communication may be held upbecause acknowledgement messages cannot be communicated in the uplinkdirection. By increasing the uplink priority of the terminal 3concerned, the throughput for this terminal, as well as the overalldownlink utilization is increased. The deterministic behaviour isanalyzed in a protocol-independent fashion, that is, no knowledge aboutany specific communication protocol is required. Therefore, the methodaccording to the invention will work for any kind of protocol, and isnot dependent on, for example, TCP.

The method according to the invention will be particularly useful forsessions having a high asymmetry between the uplink and the downlink.This is the case, for example, if a user is downloading information fromthe network or uploading information to the network. It is also the casefor a user retrieving e-mail from the network. The amount of data to betransmitted in the downlink direction is generally large, whereas onlysmall orders and acknowledgements need to be transmitted in the uplinkdirection. The correlation between the uplink and the downlink trafficrate for a particular session is generally relatively constant overtime.

The basic solution according to the invention is to detect thecorrelation between the downlink bitrate and the uplink bitrate for eachtraffic session and use this as input to the scheduling decision.

A more detailed description of how this may be achieved is given in FIG.2. In step S1 the ratio between the UL and the DL bit rate for eachtraffic session is calculated. A strong correlation between uplink anddownlink throughput for a traffic session is assumed, and the followingratios are calculated:

ul_ratio=ul_throughput/(ul_throughput+dl_throughput)

dl_ratio=dl_throughput/(ul_throughput+dl_throughput)

where ul_throughput is the throughput in the uplink for a particulartraffic session and dl_throughput is the throughput in the downlink forthe same traffic session. Further, ul_ratio=1−dl_ratio.

The ratios should be averaged over time to decrease the effects of theburst character of the communication. Preferably, the ratios aremaintained as a form of smoothed moving average.

In step S2 any overload or congestion situation on an uplink or downlinkconnection is identified. To do this, the total traffic is monitoredusing methods known per se. Overload occurs, for example, if the qualityof service promised to certain users cannot be achieved. In this case,the resources allocated to other users may have to be limited to achievethe appropriate quality of service. Congestion occurs if there is somuch traffic that some traffic is effectively blocked. Congestion maytherefore be seen as an extreme form of overload. Generally in thisdocument the term overload is used both for overload and for congestionas defined above.

In step S3 the course of action is determined in dependence of theoverload situation. If overload was detected on the uplink, go to stepS4; if overload was detected on the downlink, go to step S5; if nooverload or congestion is detected, go to step S6.

Step S4: Decrease the downlink scheduling priority for users having ahigh ul_ratio. Go to step S6.

Step S5: Decrease the downlink scheduling priority for users having ahigh dl_ratio. Go to step S6.

Step S6: Identify any spare capacity on the uplink or downlinkconnection. This is done by monitoring the traffic using methods knownper se.

Step S7: Determine the course of action in dependence on the capacitysituation. If spare capacity is found on the uplink, go to step S8; ifspare capacity is found on the downlink, go to step S9; if no sparecapacity is found, or if spare capacity is found on both the uplink andthe downlink: end of procedure.

Step S8: Increase the downlink scheduling priority for users having ahigh ul_ratio.

Step S9: Increase the uplink scheduling priority for users having a highdl_ratio.

Steps S1-S5 and steps S6-S9, respectively, may be performed as twoseparate methods, or the method could start with step S6-S9 and continuewith steps S1-S5. The two methods may also be carried out in parallel.

The procedure may be carried out continuously based on an autoloop, orat regular time intervals, to provide input information to thescheduling decisions. The procedure may also be carried out at irregularintervals, determined based on the traffic rate, the occurrence ofoverload or any other parameter. The scheduler may perform one or bothmethods S1-S5 and S6-S9 for each packet that is to be transmitted.

As mentioned above, the scheduling node may make scheduling decisionsbased on the information obtained according to the invention, incombination wither information used for scheduling. Such otherinformation may for example be the radio performance, that is, channelquality etc. Information regarding individual flows may be obtained fromlayers 3 and 4 (for example, TCP and IP) to prioritize traffic on a perflow basis. The inventive method may be applied only to certaintransport protocols (for example, TCP). Information about the protocolsused can be found in the protocol identifier field of the IP header.Traffic may also be scheduled based on the application used, such aswww, FTP, outlook exchange synchronization, etc. Information about theapplications may be obtained from the traffic flow (for example, TCPand/or UDP port numbers).

1. A control node for use in a wireless communication network, forallocating network resources to at least one communication session inthe wireless telecommunications network, comprising resource allocationmeans for allocating resources to the at least one session in dependenceof traffic load information regarding the traffic load in the uplink anddownlink directions in the network, and an ul_ratio and a dl_ratio percommunication session for the at least one communication session, givenasul_ratio=ul_throughput/(ul_throughput+dl_throughput)dl_ratio=dl_throughput/(ul_throughput+dl_throughput) whereinul_throughput is the throughput in the uplink for the at least onecommunication session and dl_throughput is the throughput in thedownlink for the at least one communication session, and the resourceallocation means is arranged to allocate resources in the uplink independence of the dl_ratio and/or allocating resources in the downlinkin dependence of the ul_ratio.
 2. A control node according to claim 1,further comprising monitoring means for obtaining traffic loadinformation about the traffic load in the uplink and downlink directionin the network, calculating means for the at least one session,determining the parameters ul_ratio and dl_ratio.
 3. A control nodeaccording to claim 1, wherein the monitoring means is arranged toidentify any spare capacity in the uplink and/or the downlink.
 4. Acontrol node according to claim 3, wherein the resource allocation meansis arranged to increase the scheduling priority in the downlinkdirection for the at least one session, if spare capacity is detected inthe uplink direction and the at least one session has a high ul_ratio.5. A control node according to claim 3, wherein the resource allocationmeans is arranged to increase the scheduling priority in the uplinkdirection for the at least one session, if spare capacity is detected inthe downlink direction and the at least one session has a high dl_ratio.6. A control node according to any one of the claim 1, whereinmonitoring means is arranged to identify overload or congestion in theuplink and/or the downlink.
 7. A control node according to claim 6,wherein the resource allocation means is arranged to decrease thescheduling priority in the downlink direction for the at least onesession if overload or congestion is detected in the uplink directionand the at least one session has a high ul_ratio.
 8. A control nodeaccording to claim 6, wherein the resource allocation means is arrangedto decrease the scheduling priority in the uplink direction for the atleast one session if overload or congestion is detected in the downlinkdirection and the at least one session has a high dl_ratio.
 9. A controlnode according to any one of the claim 2, wherein the calculating meansis arranged to calculate the ul_ratio and the dl_ratio as average valuesover a certain period of time.
 10. A control node according to claim 9,wherein the calculating means is arranged to calculate the ul_ratio andthe dl_ratio as smoothed moving averages.
 11. A method of allocatingnetwork resources to at least one communication session in a wirelesstelecommunications network, comprising the steps of monitoring thetraffic load in the uplink and downlink direction in the network, forthe at least one session, determining the parameters ul_ratio anddl_ratio, given asul_ratio=ul_throughput/(ul_throughput+dl_throughput)dl_ratio=dl_throughput/(ul_throughput+dl_throughput) whereinul_throughput is the throughput in the uplink for the at least onecommunication session and dl_throughput is the throughput in thedownlink for the at least one communication session, and allocateresources to the at least one session in dependence of the traffic loadand ul_ratio and dl_ratio, by allocating resources in the uplink independence of the dl_ratio and/or allocating resources in the downlinkin dependence of the ul_ratio.
 12. A method according to claim 11,wherein the step of monitoring the traffic load in the network comprisesidentifying any spare capacity in the uplink and/or the downlink.
 13. Amethod according to claim 12, comprising the step of, if spare capacityis detected in the uplink direction and the at least one session has ahigh ul_ratio, increasing the scheduling priority in the downlinkdirection for the at least one session.
 14. A method according to claim11, comprising the step of, if spare capacity is detected in thedownlink direction and the at least one session has a high dl_ratio,increasing the scheduling priority in the uplink direction for the atleast one session.
 15. A method according to any one of the claim 11,wherein the step of monitoring the traffic load in the network comprisesidentifying overload or congestion in the uplink and/or the downlink.16. A method according to claim 15, comprising the step of, if overloador congestion is detected in the uplink direction and the at least onesession has a high ul_ratio, decreasing the scheduling priority in thedownlink direction for the at least one session.
 17. A method accordingto claim 15, comprising the step of, if overload or congestion isdetected in the downlink direction and the at least one session has ahigh dl_ratio, decreasing the scheduling priority in the uplinkdirection for the at least one session.
 18. A method according to anyone of the claim 11, wherein the ul_ratio and the dl_ratio arecalculated as average values over time.
 19. A method according to claim18, wherein the ul_ratio and the dl_ratio are calculated as smoothedmoving averages.
 20. (canceled)